java - URLConnection 不遵守 ReadTimeout

Question

我在我的代码中使用了 URLConnection。我已将 ReadTimeout 设置为 5 秒，但它没有生效。当我关闭 wifi 时，会立即调用 IO 异常。

 URLConnection conn;     
 conn = new URL(StringUrls[0]).openConnection();
 conn.setReadTimeout(5000);
 in = conn.getInputStream();


      try {
           len = in.read(buffer);
           bufOutstream.write(buffer, 0, len);
           bufOutstream.close();
         } catch (IOException e1) {
             e1.printStackTrace();
                        }

IO 异常:

12-17 12:41:35.332  12761-13268/com.app.example W/System.err﹕ java.net.SocketException: recvfrom failed: ETIMEDOUT (Connection timed out)
12-17 12:41:35.362  12761-13268/com.app.example W/System.err﹕ at libcore.io.IoBridge.maybeThrowAfterRecvfrom(IoBridge.java:542)
12-17 12:41:35.362  12761-13268/com.app.example W/System.err﹕ at libcore.io.IoBridge.recvfrom(IoBridge.java:506)
12-17 12:41:35.362  12761-13268/com.app.example W/System.err﹕ at java.net.PlainSocketImpl.read(PlainSocketImpl.java:488)
12-17 12:41:35.362  12761-13268/com.app.example W/System.err﹕ at java.net.PlainSocketImpl.access$000(PlainSocketImpl.java:46)
12-17 12:41:35.362  12761-13268/com.app.example W/System.err﹕ at java.net.PlainSocketImpl$PlainSocketInputStream.read(PlainSocketImpl.java:240)
12-17 12:41:35.362  12761-13268/com.app.example W/System.err﹕ at java.io.BufferedInputStream.read(BufferedInputStream.java:304)
12-17 12:41:35.362  12761-13268/com.app.example W/System.err﹕ at libcore.net.http.UnknownLengthHttpInputStream.read(UnknownLengthHttpInputStream.java:41)
12-17 12:41:35.362  12761-13268/com.app.example W/System.err﹕ at java.io.InputStream.read(InputStream.java:163)

Answer 1

示例代码如下，

它将尝试最多 20 次以读取正确的数据。

如果一次出现异常，则5秒后重试。

private static int currentRetryCount = 0;

public static void main(String[] args) throws InterruptedException {
    retryRead(20);
}

public static void retryRead(int maxRetryCount) throws InterruptedException {
    if (currentRetryCount <= maxRetryCount) {
        try {
            System.out.println("try count " + currentRetryCount);
            URLConnection conn;
            conn = new URL("").openConnection();
            conn.setReadTimeout(5000);
            conn.getInputStream();
            // if nothing happens,it just return
            return;
        } catch (Exception e) {
            // if exception raises,it will try again after 5 seconds
            Thread.sleep(5000);

            currentRetryCount++;
            retryRead(maxRetryCount);
        }
    }
}